In recent years, there has been a strong demand for thermoplastic resins having high heat resistance and permitting easy melt processing in the fields of the electronic and electrical industry and the automobile, aircraft and space industries. As polymers satisfying such a requirement, there have been proposed various kinds of arylene thioether ketone polymers containing both aromatic ketone units and aromatic thioether units in their polymer skeletons. For example, polymers having the following structural formula [I], [II], [III] or [IV] are known (Japanese Patent Application Laid-Open Nos. 58435/1985, 124/1989, 200127/1986, 197634/1986 and 27434/1987): ##STR1##
These arylene thioether ketone polymers (hereinafter abbreviated as "PATK"s) have a high melting point and hence involve a drawback that their melt processing temperatures are high accordingly, so that they tend to loss their crystallinity or to undergo crosslinking and/or carbonization, resulting in a rapid increase in melt viscosity, upon their melt processing.
In order to improve the above drawback, it is disclosed in U.S. Pat. No. 4,812,552 to bring a poly(arylene sulfide-ketone) into contact with calcium cations, and U.S. Pat. No. 4,792,481 discloses prepregs formed of a high-molecular weight poly(arylene sulfide-ketone) resin containing a certain amount of calcium therein.
It was however found from the experiments of the present inventors that calcium ions have an effect to improve the melt stability of the poly(arylene sulfide-ketone), but strongly interact on the poly(arylene sulfide-ketone), so that its crystallization speed and degree of crystallinity are lowered. Therefore, molded or formed products from such a resin become slow in their solidification upon injection molding or the like, and hence its molding or forming cycle cannot but require a lot of time, leading to inefficient production. The resin also has a great drawback from the viewpoint of practical use that its physical properties such as heat resistance are impaired.
It is disclosed in U.S. Pat. No. 4,795,479 to add a basic compound typified by the hydroxide or oxide of a Group IIA metal of the periodic table to a block copolymer containing at least one arylene sulfide-ketone block so as to improve the melt stability of the copolymer. However, this process also involves the foregoing problems.
On the other hand, for example, poly(p-phenylene thioether) as a poly(arylene thioether) (hereinafter abbreviated as "PATE") is used as a high-performance engineering plastic having excellent heat resistance and solvent resistance. PATE is obtained by reacting dichlorobenzene, which is a monomer very cheap and industrially available, with sodium sulfide (U.S. Pat. No. 3,919,177). However, its crystalline melting point is about 285.degree. C. and its glass transition point (Tg) is also as low as about 85.degree. C. There is thus a demand for development of polymers having a higher melting point and a higher Tg.
In order to solve the above problems, it has also been proposed to react an aromatic thioether with phosgene or an aromatic dicarboxylic acid dihalide in the presence of a Lewis acid in an aprotic solvent, thereby obtaining polymers having respective predominant recurring units of the following structural formulae [V] and [VI] (Japanese Patent Application Laid-Open Nos. 104126/1985 and 120720/1985): ##STR2## However, the resulting polymers have a low degree of polymerization and poor melt stability.